Recently, house owners have been encouraged to install a solar cell system on the roof of their house to make effective use of solar energy without any adverse effect on the environment and ecosystem, and thereby to be self-sufficient in electricity consumed in their house.
For the purpose of this kind, use is made of solar cell panels of a waterproof structure wherein the solar cells are placed inside the panel, so as to prevent accidents caused by water, such as electric leakage or short-cut. These solar cell panels are standardized in such a size that a panel would give a certain voltage or power and would have a given number of solar cells arrayed inside the panel. The surfaces of solar cells are covered by a solar cell glass plate, which is a component of the solar cell panel, and are sealed with an adhesive material such as ethylene vinyl acetate (EVA).
These solar cell panels are laid on the roof by means of support members, with space maintained between the panels and the roof. This space is open to the outside so that air in the space can be replaced with outside air. Thus, the solar cell panels are cooled by the air flow through this space, and are prevented from decreased efficiency of power generation.
In these solar cell panels, there is a possibility that EVA may catch fire as it is heated from the eaves side or through the roof bed.
Recently, published Japanese Patent Application No. 8-284350 made a rational proposal on the materials and operation for bringing to completion a solar cell roofing structure in which the aforementioned solar cell panels themselves are used as the roofing material (i.e., as the roof tiles).
As shown in FIGS. 11 and 12, the roofing bed 3 of the house B mainly comprises a roofing material 7 laid over the entire surface of roof board 6 which is supported on rafters 5. A plurality of solar cell panels A are installed on this roofing bed 3.
The solar cells 1 are disposed under transparent tempered glass plate 8 to prevent the solar cell panels A from being broken when roofers walk on the panels. Metal sheets 2 are placed under the solar cells 1 in such a manner as to leave the bottom of the solar cells 1 untouched by the metal sheets 2. Aluminum beads 9 having a U-shaped cross-section are fitted to all the edges of the tempered glass plate 8. The aluminum bead 9, the solar cell 1, and the metal sheet 2 are adhered to one another and integrated by an adhesive 10. Each solar cell panel A is a rectangle in the plan view. Along the longitudinal side of the metal sheet 2, which is a component of the solar cell panel A, there is provided a connecting part 11 having a U-shaped cross-section. The connecting part 11 is disposed so that it is extended outward from the position of U-shaped aluminum bead 9. Wire connectors 4 are disposed on both ends of the metal sheet 2 along the lateral side. One of the wire connectors 4 is extended outward from the side edge of the metal sheet 2. The other wire connector 4 on the metal sheet 2 of the solar cell panel A is disposed so that the connector 4 is in a position inward from the side edge of the metal sheet 2. In this way, the wire connector from the upper panel and the wire connector from the lower panel are disposed in the positions connectable with each other, when a solar cell panel A on the upper side is butt-jointed with a solar cell panel A on the lower side.
FIG. 11 shows the wiring extending from a solar cell 1. The wire 12 is led through the metal sheet 2 to its downside and is connected with the wire connector 4, which is disposed at the end of the metal sheet 2.
The space between the solar cells 1 and the metal sheet 2 constitutes an air flow channel 13 for cooling the solar cell panels. The aluminum bead 9 fitted along the lower edge of each solar cell panel A has a covering portion 9a extended from the upper surface of the bead 9. The aluminum bead 9 fitted along the upper edge of each solar cell panel A has a receiving portion 9b extended from the lower surface of the bead 9. When an upper panel and a lower panel are laid adjacently to each other in the direction of roof slope, the covering portion 9a of the lower bead 9 fitted to the upper panel is engaged with the receiving portion 9b of the upper bead 9 fitted to the lower panel, with a coking material 14 being filled in between, so that the water-tightness is secured in the connected area.
When panels are laid side by side in a direction perpendicular to the roof slope, the panels A are disposed in such a way that a rafter 5 always comes under each connecting portion 11 of the metal sheet 2 provided along the longitudinal side of the panel A. Thus, one connecting portion 11 of a panel sits on a rafter 5 side by side with the other connecting portion 11 of the next panel. The two adjacent connecting portions 11 are covered with a metal fitting 15 having a reverse U-shaped cross-section. This metal fitting 15 is fixed to the rafter 5 via roof bed 3 by using a fixture 16, so that the panels can be connected to one another. The part 17 is an inner cap having a reverse U-shaped cross-section, disposed inside the metal fitting 15 and used to cover directly the two connecting portions 11. On the metal fitting 15 is fitted a cap 18, which fills the gap between the two aluminum beads 9 of solar cell panels A disposed side by side in a direction perpendicular to the roof slope.
The above-described solar cell panel A is provided with a non-inflammable material, such as the metal sheet 2, under the solar cells 1, with a space left between the solar cells 1 and the metal sheet 2. Due to this non-inflammable material, the solar cell panels are protected against fire coming from the eaves side or from the roof bed. The space between the solar cell 1 and the non-inflammable material (i.e., the metal sheet 2) can also be utilized as a vent for the gas evolving from the filler in the solar cells 1 at the time of production and/or operation of solar cells 1. Because the non-inflammable material is integrated in the solar cell panel, the solar cell roof of a fireproof, non-inflammable structure can easily be formed, which is protected against fire coming from the eaves side or through the roof bed, by setting up the solar cell panels A, one after another on the roof.
As described above, the prior-art solar cell panels can be certainly utilized as a roofing material by supporting the panels on a fireproof, non-inflammable material in such a way as to secure a cooling air flow channel. However, for the weathering at the joints between panels laid in the roof slope direction, the gap is filled with a coking material. It is commonly known that of all the areas of a house, the roof is a place most severely affected by the wind, the rain, and the sunlight. In existing tile roofs, the most important weathering is secured by laying roof tiles in an overlapping manner. It is not technically reasonable to think that the weathering can be guaranteed by coking, without overlapping the roofing material.
The solar cell panels are manufactured by protecting the panel edges with the aluminum bead 9, are integrated with the non-inflammable supporting material by adhering the supporting material to the bordering areas on the lower surface of the panel, and are brought in to the site in packages. In such assemblies, it is not necessary to protect the panel edges with the aluminum bead 9 which is usually used on the premises that the panel is dealt with as a single material. (The two beads 9 serve to receive the cap 18.) Such a panel assembly incurs a higher cost of production than a necessary level.
Furthermore, the cap 18 serves as a means of weathering between the two adjacent roofing materials in the direction of the roof slope. This weathering merely involves pushing the cap 18 into the gap between the two aluminum beads 9. In this case, it is assumed that rainwater is allowed to creep into the grooves formed by the connecting portions 11. In a structure allowing water to get inside the gap, a serious situation may be brought if the drainpipe is clogged.